When I was using Ubuntu, I installed pommed to control the LCD brightness and keyboard backlight and eject key, etc.
In Gentoo, I discovered the ebuild for pommed is horribly outdated so I built pommed from source.

Pommed can successfully change my keyboard backlight and I was able to reverse the function key with it also.
However, I am still unable to change the brightness of the screen.

This is not a problem with pommed. I emerged nvclock and it is also unable to change the brightness.
After that, I emerged macbook-backlight and it is also useless:

Code:

macbook-backlight -s 100
error, cannot find video card

I know that all three programs access some files in /sys (or was it proc?) to change the brightness but the files don't exist. There is nothing related to the lcd backlight in /sys. The only thing I could find was "kbd_backlight" which is for the keyboard backlight. Any ideas why the relevant files are missing?

According to lspci, I have 2 GPUs: intel HD and NVIDIA GeForce GT 330M.
I am using the nouveau driver.

CONFIG_FB_BACKLIGHT=y
CONFIG_BACKLIGHT_LCD_SUPPORT=y
CONFIG_BACKLIGHT_CLASS_DEVICE=y
CONFIG_BACKLIGHT_GENERIC=y
# CONFIG_BACKLIGHT_PROGEAR is not set
CONFIG_BACKLIGHT_APPLE=y
# CONFIG_BACKLIGHT_SAHARA is not set
# CONFIG_BACKLIGHT_ADP8860 is not set
# CONFIG_BACKLIGHT_ADP8870 is not set
# CONFIG_LEDS_TRIGGER_BACKLIGHT is not set
CONFIG_DRM_NOUVEAU_BACKLIGHT=y

EDIT: I just took a look at the config for Ubuntu (pommed worked there before) and discovered it had several more BACKLIGHT options, including CONFIG_FB_NVIDIA_BACKLIGHT.
Additionally, I discovered that CONFIG_FB_NVIDIA_BACKLIGHT is hidden in "make menuconfig" unless nvidia framebuffer support is activated.
I'm recompiling the kernel as I speak..........type, I'm recompiling the kernel as I type.